I went back and forth with glass arriers for 4x5 and finally decided that there are trade offs both ways. I have taken the easy route and use a glassless carrier and am very happy. EC
Sometimes it just doesn't pay to overthink the small stuff...
I highly doubt it. This is the 2mm thick glass Schneider uses in B+W MRC filters (they claim the coating is actually harder than the glass). It was a reasonable cost for 35mm. Schneider cut two rectangles for me out of two clear MRC camera filters. But for anything bigger I can only imagine what this would cost. Not only that, I don't even know if they put that coating on glass big enough for anything larger than medium format film (beyond a certain filter ring size they don't seem to offer that coating - at least on any standard products). There's no way they'd have this stuff big enough for 8x10, let alone 11x14. It would have to be much thicker obviously. You're probably best off with Focal Point. I'm thinking of trying some of their stuff out.
Originally Posted by Bob Carnie
[QUOTE=DREW WILEY;1329140] For smaller originals
(4X5 down) the wavy pattern Omega and Durst style glass works quite well. QUOTE]
Drew, Focal Point AN glass is no good for 4x5? I'd be interested in it for the top glass. My enlarger is a Saunders/LPL 4550. The AN glass in their carriers looks like junk. I might be wrong though.
I did not say Focal Point AN was unusable for 4X5, but implied how the function of potential choices
is related to other specifics, such as the degree of diffusion of the light source, the contrast level,
depth of field, and focal length relative to format. Focal Point is easy to deal with and affordable, and I certainly wouldn't want to discourage anyone from trying their product. Most often the kind of
problem I encounter with AN texture would be printing onto a very hard paper grade from a med format negative, which sometimes happens because one can't individually process each shot like in
sheet film. Raise the contrast high enough and something inevitably shows thru; and silver grain in
black and white film is more likely to interact with this effect than dye clouds in color film.
Bob - wish I knew what that Zeiss glass I bought a ctn of long ago was originally meant for. It's got
a smooth coating which is highly abrasion resistant and somewhat suppresses rings, but it's not a
typical optical coating. About 2mm and fairly tough (took me 20 yrs to finally break a piece). In cutting behaves like tempered glass. Very flat optically. Odd size, metric, but almost 12x16. The Zeiss part number hasn't led me anywhere so far. Maybe not suitable for high UV transmission, but
works perfectly for ordinary VC blue filter split printing.
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I think it is best to use coated glass under the neg and anti-newton glass over the neg. If you step back and think about it for a second, why wouldn't you want nearly 100% transmission instead of 90ish? The refracted light has to go somewhere....
I have done this with a 35mm enlarger and the results were perceptively (albeit slightly) better. I keep meaning to order AR glass from Edmunds to put in my Saunders 4x5 carrier that I use for all formats. I'll just need to find someone who can cut it, if anyone has any suggestions.....
I would love to replace the bottom glass with Schott coated glass. That would be the shiznit...
Focal Point cuts glass in many different sizes. It also comes nicely beveled. I imagine they could cut it in any size you need. The set of their glass I bought for the Durst 138 is also optically white and thinner than window glass (2mm I think). Very good stuff in my opinion. But I don't know if a ground sheet could be optically better. Probably, but I doubt I could see it since I see no issues with the Focal Point stuff at my small enlargement sizes (20x24 from 4x5).
Originally Posted by Bob Carnie
Focal Point offers different thicknesses and can cut to any reasonable size.
I'd recommend 2mm for most carriers and 3mm for ULF contact frames.
Schott glass would be quite expensive. You can get optically coated picture
frame glass fairly reasonably, but it's more fragile and its difficult to cut and edge. I recommend the titanium coated type rather than the original
magnesium fluoride Denglas which is no longer made. Don't confuse this with etched nonglare glass. And it needs to be specially cleaned, just like a lens. Don't grab a bottle of Windex. Someone still owes me a lot of
Schott enlarger glass, but they haven't made good. I suspect they just couldn't get it themselves, despite still advertising it. I don't think Edmund
is a good source for this kind of thing, though their big industrial catalog is
an excellent resource for a variety of other useful things. Ignore the hobby
catalog and related website. The world's biggest optical coating lab used to be just across the Bay, and they could custom do just about anything,
but got bought out and relocated.
Thanks Drew. AN texture showing through is exactly the thing I wrestled with when using AN glass above the negative. That's why I eventually scrapped it. I guess you're right it takes experimentation with different kinds - unfortunately I just wish there was an easier solution (aside from my TXP trick). For what it's worth, when I enlarge 4x5 negatives it is usually only to 8x10 or max 11x14, and I can't remember the last time I needed higher than about grade 3. So maybe that will help.
Also didn't realize 2mm could potentially be strong enough for sheet film. That makes things a little more interesting. For the fun of it I will ask Schneider how big a piece of MRC glass they could do. They didn't bevel it when they cut it for me though.
Bob et al: Is it 100% necessary to be bevelled? Is this a safety thing? Or some other reason?
I also need to follow up with John Sexton - a few months back he told me he was about to experiment with a different type of anti-reflection glass that was supposed to avoid Newton rings. I wonder how that went.
M. Lointain: Shiznit for sure! My 35mm carrier for my 4x5 Saunders has multicoated ("Multi Resistant Coated") Schott glass (from B+W MRC clear filters). Love it!
What about using the Tru Vue Museum glass in a carrier? Looks like it's coated.